The present invention relates to oil pumps for use in motor vehicles to supply lubricating oil, drive hydraulic actuators, etc.
U.S. Pat. No. 4,767,296 discloses an oil pump for supplying lubricating oil in motor vehicles. This oil pump is of the trochoidal type including an inner rotor and an outer rotor eccentrically disposed at the outer periphery thereof, wherein trochoid-curve-based external teeth and internal teeth are formed on an outer peripheral surface of the inner rotor and an inner peripheral surface of the outer rotor, respectively. The number of internal teeth of the outer rotor is larger by one than that of the external teeth of the inner rotor. A plurality of pump houses defined between the internal and external teeth is urged to move circumferentially with rotation of the inner rotor for variation in volume of each pump house.
The above trochoidal oil pump raises no problem such as noise, vibration and wear at high-speed rotation, but produces a great loss of driving horsepower at low/medium-speed rotation for the reason as described later.
It is, therefore, an object of the present invention to provide oil pumps for use in motor vehicles, which allow a restraint in noise, vibration and wear at high-speed rotation and a reduction in consumed horsepower at low/medium-speed rotation.
The present invention provides generally an oil pump, comprising:
a housing;
a pump portion accommodated in the housing, the pump portion being rotated with both sides closed by sidewalls of the housing, the pump portion including a plurality of pump houses arranged circumferentially, the pump houses being urged to move in a direction of rotation for variation in a volume thereof;
suction and discharge chambers formed in the sidewall of the housing, the suction and discharge chambers facing suction and discharge areas of the pump portion, respectively;
a maximum-volume-side partition area formed with the sidewall of the housing on a trajectory of the pump houses and at a position where each pump house has a maximum volume, wherein the maximum-volume-side partition area creates a section where any pump house fails to spread over either of the suction and discharge chambers; and
a plurality of channels arranged in the discharge chamber at an end thereof, each channel having a predetermined length and extending to the maximum-volume-side partition area.